Togaware DATA MINING
Desktop Survival Guide
by Graham Williams
Google

Map Data

R provides a set of tools for reading geographic (map) data, particularly ESRI http://en.wikipedia.org/wiki/Shapefileshapefiles, and plotting and manipulating such data. Maps for many countries are available, particularly the US, Europe, and New Zealand. Limited Australian map data is also freely available.



download.file("http://www.vdstech.com/mapdata/australia.zip", "australia.zip")
system("unzip australia.zip; rm australia.zip")

http://rattle.togaware.com/code/get-australia.R

The data can be read in with readShapePoly and displayed with plot. Australia has a few outlying islands which we crop from the main focus of the map here using xlim and ylim.

[width=0.8]map-australia-plot


library(maptools)
aus <- readShapePoly("australia.shp")
plot(aus, lwd=2, border="grey", xlim=c(115,155), ylim=c(-35,-20))
dev.off()

http://rattle.togaware.com/code/map-australia-plot.R

The class of the resulting object (aus) is SpatialPolygonsDataFrame. Such an object has a collection of slots. For example, the data slot includes meta information about the region recorded in the data frame.



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  FIPS_ADMIN GMI_ADMIN                   ADMIN_NAME FIPS_CNTRY CNTRY_NAME
0       AS01   AUS-ACT Australian Capital Territory         AS  Australia
1       AS02   AUS-NSW              New South Wales         AS  Australia
2       AS03   AUS-NTR           Northern Territory         AS  Australia
3       AS04   AUS-QNS                   Queensland         AS  Australia
4       AS05   AUS-SAS              South Australia         AS  Australia
5       AS06   AUS-TSM                     Tasmania         AS  Australia
6       AS07   AUS-VCT                     Victoria         AS  Australia
7       AS08   AUS-WAS            Western Australia         AS  Australia

                 REGION CONTINENT POP_ADMIN  SQKM_ADMIN SQMI_ADMIN  TYPE_ENG
0 Australia/New Zealand Australia    292475    2342.295     904.36 Territory
1 Australia/New Zealand Australia   6338919  803110.812  310081.09     State
2 Australia/New Zealand Australia    161294 1352365.000  522148.09 Territory
3 Australia/New Zealand Australia   3107362 1733475.000  669294.69     State
4 Australia/New Zealand Australia   1445153  985308.500  380427.59     State
5 Australia/New Zealand Australia    472122   68131.477   26305.56     State
6 Australia/New Zealand Australia   4354611  227781.406   87946.40     State
7 Australia/New Zealand Australia   1655588 2533628.000  978233.81     State

   TYPE_LOC
0 Territory
1     State
2 Territory
3     State
4     State
5     State
6     State
7     State

The bounding box of the plot is available using bbox.

> bbox(aus)
         min       max
r1 112.90721 159.10190
r2 -54.75389 -10.05139



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